Kinetic signatures of the region surrounding the X-line in asymmetric (magnetopause) reconnection

TL;DR

This study uses kinetic simulations to identify key signatures of the electron diffusion region during asymmetric magnetic reconnection, revealing electric field structures, electron distributions, and plasma property variations near the X-line.

Contribution

It provides new kinetic signatures and detailed electron distribution characteristics associated with the EDR in asymmetric reconnection, enhancing understanding of reconnection physics.

Findings

Shoulder in sunward electric field indicates EDR presence

Crescent-shaped electron distributions form near the X-line

Magnetosheath properties are lower upstream of the X-line

Abstract

Kinetic particle-in-cell simulations are used to identify signatures of the electron diffusion region (EDR) and its surroundings during asymmetric magnetic reconnection. A "shoulder" in the sunward pointing normal electric field (EN > 0) at the reconnection magnetic field reversal is a good indicator of the EDR, and is caused by magnetosheath electron meandering orbits in the vicinity of the x-line. Earthward of the X-line, electrons accelerated by EN form strong currents and crescent-shaped distribution functions in the plane perpendicular to B. Just downstream of the X-line, parallel electric fields create field-aligned crescent electron distribution functions. In the immediate upstream magnetosheath, magnetic field strength, plasma density, and perpendicular electron temperatures are lower than the asymptotic state. In the magnetosphere inflow region, magnetosheath ions intrude resulting in an Earthward pointing electric field and parallel heating of magnetospheric particles. Many of the above properties persist with a guide field of at least unity.